Percussive drill



1.. w. GREVE 1,891,411

PERGUSSIVE DRILL Filed Feb. 24, 1928 Patented Dec. 20, 1932 UNITED. STATES PATENT mm; 7

LOUIS w. GBEVE, or CLEVELAND, omo, ASSIGNOR To THE. CLEVELAND noon DRILL COMPANY, or CLEVELAND, onro PERCUSSIVE DRILL Application filed February 24, 1928. Serial No. 256,614.

The present invention is directed to improvements in percussive drills of the valveless type.

The primary object of the invention is to provide a device of this character so constructed that a relatively large supply of inotive fluid. will be maintained in the rear of the large head of the differential piston for action thereon to more eflectively move the same on its forward or working stroke, the

same fluid also aiding in cushioning the piston on its rearward stroke.

Another object of the invention is to provide a device of this kind which will deliver a powerful working blow, and one which is simple in construction, eflicient in operation, durable, and which will operate with a minimum amount of fluid.

lVith these and other objects in view, this invention resides in the novel features of con struction, formation, combination and arrangement of parts to be hereinafter more fully described, claimed, and illustrated in the accompanying drawing, in which The figure represents a longitudinal sectional view through the device.

Referring to the drawing, 1 designates the back head of a percussive drill and 2 the cylinder which is coupled thereto in any 0 approved manner. Interposed between the front head 8 and the cylinder 2 is a tappet case 4 having associated therewith the tappet 5 for striking the drill steel 5.

The cylinder 2 is formed with front and I rear piston chambers 6 and 7, respectively,

the former being of greater diameter than the latter, the purpose of which will be later explained. The rear end of the smaller piston chamber opens into a distributing chainher 8 which is formed in the back head 1, motive fluid being conducted thereto through the passage 9 leading from a source of compressed air. The back head is further provided with a centrally located pocket 10 which opens into the chamber 8, the purpose of which will later appear.

Mounted for reciprocation in the cylinder is a iston 11 which consists of a large head '12 s idable in the large chamber 6 and a smaller elongated head 13 slidable in the chamber .7, the lattertheaid being of such length that on its rearward stroke the rear end thereof will enter the distributing chamber 8 and also the pocket 10.

The heads12 and 13 are connectedby a reduced neck 14: which. produces an annular groove 15 between the respective heads.

In the rear end ofthe chamber 6 is formed an annular chamber constituting 'a reservoir 16 in which a relatively large supply of mo tive fluid is stored for acting against the "rear face of the head 12. 1

A longitudinally extending motive fluid conducting passage 17 is formed in the cylinder wall and connects with the front end of thepiston chamber -6'through aport'. 1-8,

whilethe rear end of said passage connects with the rear end of the chamber 7 f through "the port 19, said passage also being in communication with the reservoir16 through a duct 20 which opens new the rear wall of said reservoir. I 1 W The cylinder wall is further provided with a relatively short'passage 21 which has its rear end openinginto the constant air chamber 8, the forward end thereof connecting with the forward end of the" chamber, 7 through the duct 22'.- The cylinder 2 is pro vided with an exh'austport" 23.

7 As shown in fullglines in the drawing, the

piston is in its forwardpositionand is about to begin its. rearward stroke, and at which time the small head has uncovered the port 19 in order that motive fluid from the chamber 8 will pass therethrough into the passage 17 and through the port 18 to act upon the front face of the large head-12 to force the same rearwardlyand against the pressure upon the rear end of the small head 13. Ob-

viously some motive fluid will pass through the duct 20- to maintain a supply: of motive fluid in the reservoir 16 in order that'a relatively large volume ofmotive fluid will be present to act vagainst'the rear faceof,

the head 12, thissame fluid also aiding in cushioning the rearward 'movement' of the piston. A flow of fluid through aperture 20 from the passage'l'i' is'cau'sed by and takes place when a back pressure is built up in the passage as the incoming motive fluid fills motive fluid in highly compressed condition head. When the groove 15 registers with the duct 22, as shown in dotted lines, motive fluid the end of the cylinder beneath the piston head 12. As the piston head 12 travels in its return stroke it covers the exhaust passage 23 and then the opening 7 into the passage 17. The motive fluid introduced into the cylinder above the piston through the orifice 2O aids in cushioning the return stroke of the piston. As soon as the opening 7 is closed by the end 11 of the piston the flow of fluid through passage 17 from the supply ceases, and the flow of fluid from the passage 17 through duct 20 into the cylinder ceases and reverses. The continued rearward travel of the piston compresses the fluid within the cylinder above the piston and causes fluid to ciprocable therein, there being passages leading to opposite ends of the cylinder, valve means on the piston for alternately directing motive fluid through said passages to the 0pposite ends of the cylinder, an auxiliary passage connecting the rear end of the cylinder with that one of said passages for conducting motive fluid to the forward end of the cylinder, an exhaust port in the cylinder arranged to be closed by the piston adjacent one end of its stroke, said port being arranged to be opened selectively to both ends by the piston. In testimony whereof I aflix my signature.

LOUIS W. GREVE.

flow thru the orifice 20, passage 17, orifice 18 and exhaust passage'23. The rate at which the fluid is so exhausted from the upper end of the cylinder is controlled very largely by the dimensions of the orifice 20, which may be such as to regulate the return motion of the piston at the desired rate. When the piston is moved in a forward direction the motive fluid introduced through'passage 22 into theadjacent end of the cylinder, escapes, to a small degree, through duct 20, passage 17 and orifice 18 through the lower end of the cylinder. Even after the passage 21 has been closed by the end 13 of the piston the in the upper end of the cylinder causes a flow of the fluidinto the forward end of the cylinder where it aids in cushioning the piston '12; The rate of that fluid flow is determined by the size of the orifices 20 and 18. As the piston continues to move rearwardly the small head will close the port 19, thus cutting off the supply of motive fluid to the front face of the head 12, exhaust taking place'through the port 23. Continued rearward travel of the piston will bring the neck 14 into the chamber 7 in order that the annular groove 15 will register with the duct 22, and at which time the rear'end of the head 13 will enter the reservoir 16 will effectively cushion the rearward movement of the piston to prevent the rear end of the head 13 striking the back the motive fluid in the chamber 8 when said :rear end leaves the pocket 10. In this man- "ner the full cross sectional area of the piston 11 is subjected to pressure inorder that the same will be driven forwardly rapidly to strike the tappet a sharp and hard blow, the tappet in turn striking the drill steel 5.

' What is claimed is A drill having a cylinder and a piston re- 

